A review of reptile research and conservation management on Tiritiri Matangi Island, New Zealand
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272 New on-line
Available Zealandat:Journal of Ecology, Vol. 37, No. 3, 2013
http://www.newzealandecology.org/nzje/
A review of reptile research and conservation management on Tiritiri Matangi Island,
New Zealand
Marleen Baling1, 2, *, Dylan van Winkel1, 3, Melinda Rixon (née Habgood)4, 5, Jonathan Ruffell6, 7,
Weihong Ji1 and Graham Ussher8
1
Institute of Natural and Mathematical Sciences, Massey University, Private Bag 102904, Auckland 0745, New Zealand
2
Pacific Invasives Initiative, IUCN Invasive Species Specialist Group, The University of Auckland, Private Bag 92019,
Auckland 1142, New Zealand
3
Bioresearches Group Ltd, P.O. Box 2828, Auckland 1140, New Zealand
4
Auckland Council, Private Bag 92300, Auckland 1142, New Zealand
5
Te Ngahere Ltd, P.O. Box 71109, Rosebank Post Centre, Auckland 1348, New Zealand
6
85 David Avenue, Manurewa, Auckland 2102, New Zealand
7
Boffa Miskell Ltd, P.O. Box 91250, Auckland 1142, New Zealand
8
Tonkin and Taylor Ltd, P.O. Box 5271, Auckland 1141, New Zealand
*Author for correspondence. (Email: m.baling@gmail.com)
Published online: 18 November 2013
Abstract: Tiritiri Matangi Island is one of the oldest community-driven island restoration projects in New
Zealand. While great effort has been directed towards recovery of vegetation and avian communities since the
1980s, restoration of the island’s reptile fauna has not been initiated until early 2000s. Tiritiri Matangi supports
only three remnant reptile species, which is considerably low given the island’s size and geographic location. In
recognition of this and the importance of reptiles in ecosystem function, translocations of several reptile species
have been undertaken. The translocations presented opportunities for integrating in-depth scientific studies
in regard to applied conservation management of native reptiles with experimental approaches. This review
summarises research efforts on Tiritiri Matangi to date, including post-graduate studies that have contributed to:
(1) baseline information on resident species (Oligosoma moco, O. aeneum, Woodworthia maculata, O. smithi
& Naultinus elegans); (2) understanding the importance of seabird co-habitation for Sphenodon punctatus;
(3) post-release behaviours (dispersal and habitat selection) of Hoplodactylus duvaucelii; (4) body colour
adaptation of O. smithi following translocation; (5) quantifying avian predation on lizard populations; and
(6) measuring the short-term success of all translocations. Numerous research opportunities remain, either
on existing populations or future translocations to the island. Emphasis has been placed on the involvement
of public and local community volunteers in all reptile research. These groups are key stakeholders in the
restoration of Tiritiri Matangi. Measurement of translocation success for New Zealand reptiles is dependent on
long-term monitoring (> 10 years) and research, since these endemic reptiles exhibit distinctive characteristics
such as slow maturity, low reproductive rates, and very high longevity. The process of restoration of a fully
functioning New Zealand ecosystem is similarly slow, therefore, long-term study or monitoring will also enable
assessment of the island’s restoration outcome over time.
Keywords: island restoration; translocation; Oligosoma; Woodworthia; Sphenodon punctatus; Hoplodactylus;
Naultinus; avian predation; monitoring
Introduction (Towns et al. 2007); and Little Barrier Island (Rayner et al.
2007; Bellingham et al. 2010)). As few of these important
The reptile fauna of New Zealand has suffered severe range offshore islands offer opportunities for easy access to rare
contractions and dramatic reductions in abundance since the species, research efforts have been somewhat limited.
arrival of humans, c. 1000 years ago (Davidson 1984; Towns One exception is Tiritiri Matangi Island, an Open
1994; Craig et al. 2000). Once widespread throughout the Scientific Reserve located approximately 4 km off the coast
country, many endemic species are now restricted to small, of the mainland Whangaparaoa Peninsula in the Hauraki Gulf
remnant, pseudo-endemic populations confined to predator- (Fig. 1), which allows easy and frequent access for both the
free offshore islands (Towns & Robb 1986; Daugherty et al. public and scientists. The island is historically important as
1990; Towns & Daugherty 1994). Currently, over half of one of the oldest community-driven island restoration projects
New Zealand’s islands are legally protected and those that are in New Zealand. Removal of mammalian pests by 1993 and
ecologically significant (and therefore of high conservation establishment of a community-driven replanting programme
value) are designated as Nature Reserves (Towns 1983). since the 1980s have resulted in extensive forest regeneration
Introduced mammals have been eradicated from some of these on the island (Drey et al. 1982; Mitchell 1985; Galbraith &
island reserves and restrictions on public access ensures that Hayson 1994; Hawley 1997; Veitch 2002). Various faunal
the islands’ biota, including reptiles, can survive and regenerate translocations to the island have led to establishment of
naturally (e.g. Mercury Islands (Towns 1991); Marotere Islands new populations of threatened species (Galbraith & Hayson
New Zealand Journal of Ecology (2013) 37(3): 272-281 © New Zealand Ecological Society.Baling et al.: Reptile research and conservation on Tiritiri Matangi Island 273
Figure 1. Location of Tiritiri
Matangi Island in the Hauraki
Gulf, Auckland, New Zealand.
1994), while associated scientific research projects have 2003, Clarke 2003). Habgood’s (2003) study estimated that
provided information on the biology, ecology and successional population densities for both species were highest in the open
changes in vegetation (West 1980; Craig & Stewart 1988; grassland areas, followed by those in young mixed-species
Cashmore 1995), invertebrate (Green 2002; Clarke 2003), planting areas. These two skink species have benefited from
reptile (Habgood 2003; Ruffell 2005; van Winkel 2008; van the eradication of mammalian predators and they appear to
Winkel & Ji 2012; Baling et al. 2013) and bird communities be capable of maintaining high population densities despite
(e.g. Galbraith & Hayson 1994; Armstrong & Ewen 2001; the high abundance of avian predators that are present on the
Ortiz-Catedral & Brunton 2009). island (Habgood 2003).
The level of research for restoration of reptile communities A remnant population of W. maculata was detected
on Tiritiri Matangi has been relatively low and has largely been relatively recently (2004) during routine biosecurity monitoring
overshadowed by studies on more charismatic avian taxa (e.g. on the island. The discovery of gecko footprints in a rodent
Colbourne & Robertson 1997; Ryan & Jamieson 1998; Jones tracking tunnel initiated a survey on the eastern cliffs (The
2000; Brunton & Stamp 2007). Additionally, early restoration Arches) and confirmed the presence of this species. Another
management of Tiritiri Matangi (Drey et al. 1982) did not reptile survey in 2006 identified additional sites that extended
take an ecosystem-wide approach and failed to recognise the distribution of W. maculata along the eastern coast of
reptiles as important elements of the environment, and thus the island (Ussher & Baling 2007). Periodic surveys of the
as candidates for translocation (with the exception of northern population are conducted by Massey University to determine
tuatara, Sphenodon punctatus). There has been an increase the population density and genetic structure. Initial results from
in support for and recognition of the role of reptiles within a mark-recapture study indicate the W. maculata population size
New Zealand ecosystems, including plant-animal interactions is larger than previously expected (W. Ji, unpub. data). This
(Whitaker 1987; Lord & Marshall 2001; Wotton 2002; Smith remnant population has persisted in the presence of introduced
2009), predator-prey dynamics (Markwell 1998; Ball & Parrish predators, particularly kiore (Rattus exulans), by surviving in
2005), and island nutrient cycling (Mulder & Keall 2001). the crevices of the coastal cliffs. However, the recovery rate
This has prompted many restoration groups to focus their of W. maculata seems to be slow, with the population still
conservation initiatives on restoring and monitoring reptile largely confined to coastal cliffs 11 years after all kiore were
communities (e.g. Ritchie 2000; Gardner-Gee et al. 2007). removed from the island.
The purpose of this paper is to describe the variety of The three other species that are either unconfirmed or
projects that have been initiated for reptile conservation considered extinct on Tiritiri Matangi are S. punctatus, shore
on Tiritiri Matangi, to discuss the scientific drivers behind skink (O. smithi) and Auckland green gecko (Naultinus
population restoration efforts and the role of public involvement elegans). Evidence for the past existence of S. punctatus on
in the long-term monitoring of scientific programmes. the island is derived from a single bone found in a midden site
(pre-dating the apparent Maori settlement on the island) during
excavations for wharf structures in the 1990s (R. Brassey,
Baseline information on resident reptiles pers. comm.). Additionally, accounts by a lighthouse keeper
of handling a live tuatara while stationed on the island in the
Prior to planning the restoration of reptile communities for a early 1900s, adds further support for the historical presence
given island, baseline knowledge of historical and current status of S. punctatus (J. Craig, pers. comm.).
of reptile populations needs to be assessed. Historically, there Sightings of several O. smithi were reported on one of
may have been at least six reptile species on Tiritiri Matangi, the beaches on the southern end of the island (Bee Bay, south
but only three species survive there today. These remnant of Wharf Beach) in 1975 (R. Hitchmough, pers. comm.).
species are the moko skink (Oligosoma moco), copper skink Lizard surveys undertaken in 2000 and 2006 failed to detect
(O. aeneum) and common gecko (Woodworthia maculata). this species, despite live-trapping and hand-searching along
Oligosoma moco and O. aeneum are the most abundant the island’s coastline (Ussher 2000; Ussher & Baling 2007).
species, and overlap in distribution across the island (Habgood As a result, this species was declared locally extinct in 2006.274 New Zealand Journal of Ecology, Vol. 37, No. 3, 2013
There have been unsubstantiated records of bright green new populations within the species’ native range. Tiritiri
geckos from several locations on Tiritiri Matangi, including Matangi has seen both reintroduction and reinforcement of
Lighthouse Valley, Little Wattle Valley and Bush 1 (Rimmer reptiles. In this paper we are using the term ‘translocation’
2004; P. Cashmore, pers. comm.; A. Rimmer, pers. comm.). to cover both types.
However, there are no records (substantiated or otherwise) Translocations are usually highly successful if approached
since these single sightings in the early 1900s. The lizard in a strategic manner (e.g. when based on a good understanding
survey in 2000 failed to detect any geckos and Ussher (2000) of the biology and habitat requirements of the species), and
concluded that any small remnant population of this species when a research component is incorporated into the project
would have declined over the years to solitary individuals. A (e.g. by using scientific or experimental design for monitoring
more extensive search for N. elegans over the summer season success) (Towns et al. 1990; Armstrong et al. 1994; Frankham
of 2007/08 (> 80 person search hours) reaffirmed the apparent 1994; Armstrong & McLean 1995; Germano & Bishop 2009).
absence of this species on the island (M. Baling, unpub. data). A strategic or scientific approach to translocation and associated
Northern offshore islands of New Zealand are historically post-release monitoring will provide the best opportunity to
and currently known to support large numbers of reptile measure success and to understand why translocations fail
species (e.g. 10 species on 13 ha Middle Island, 9 species on (e.g. unsuitable habitat quality, disease, predation, competition
100 ha Stanley Island, 10 species on 138 ha Lady Alice Island, or homing behaviour; Armstrong et al. 1994; Germano &
and 12 species on 1509 ha Motutapu Island; Whitaker 1978; Bishop 2009). Lessons learnt can then be fed back into the
Towns & Ballantine 1993), and most of these species often species management strategy in an adaptive process, or be
occur naturally at high densities (e.g. Towns 1996; Markwell applied in any future translocation plans for the same island
1997). Therefore, Tiritiri Matangi at 220 ha, could potentially (Armstrong et al. 2007).
have supported reptile diversity and densities similar to those Translocations also offer the potential to conduct more
other islands. The current fragmented distribution of reptiles in-depth research on a species or an ecological process that
at Tiritiri Matangi also suggests that several of the island’s is otherwise rare or isolated (Parker 2008). A translocation
ecological niches are unoccupied. Based on the fauna of can be designed where animals are released under specific
adjacent islands (Towns & Ballantine 1993; Miller et al. experimental conditions to test particular hypotheses.
1994; Towns et al. 2001; Towns et al. 2002), Tiritiri Matangi Designing such experiments can be challenging, but they are
should be capable of supporting species such as O. suteri an effective way to maximise the opportunity and success of
(egg-laying skink) in beach habitats; Dactylocnemis pacificus translocation programmes over the long-term.
(Pacific gecko) and Hoplodactylus duvaucelii (Duvaucel’s As part of the process of planning for successful restoration,
gecko) in forest edge habitats; and O. ornatum (ornate skink), problems that might arise from translocating new species of
Mokopirirakau granulatus (forest gecko), S. punctatus and reptiles to Tiritiri Matangi need to be anticipated and addressed.
O. whitakeri (Whitaker’s skink) in forest habitats. Several initial topics of interest are: 1) inter-specific competition
(the ‘incumbent advantage’ of resident species over introduced
species); 2) ecological requirements of translocated species
Scientific approach to translocations (habitat quality and selection, behavioural responses to
transfer); and 3) avian predation (survival probability of the new
Reptiles represent a large portion of the faunal biodiversity of species if introduced into high-density bird populated sites).
New Zealand (Towns & Daugherty 1994), and therefore, are
expected to have a strong influence on New Zealand ecosystems Population establishment and interspecific competition
(Walls 1981; Whitaker 1987; Spencer et al. 1998; Lord & The two resident skink species on Tiritiri Matangi Island,
Marshall 2001; Payton et al. 2002). In the absence of reptiles O. moco and O. aeneum, exist within similar habitat and
(e.g. due to introduced mammalian predators), some ecological locations, are both diurnal generalist foragers, and have similar
interactions can be supressed or lost (Whitaker 1973; Towns reproductive ecologies (Habgood 2003). Concerns were
2002; Hoare et al. 2007). Therefore, pest eradication alone raised regarding the difficulty a translocated lizard population
may be insufficient to regenerate a functioning ecosystem if might have when trying to establish in the presence of resident
there are missing links in the biotic diversity of that island. lizards. A resident species may have an advantage (e.g. by
This recognition has been an impetus for active conservation being abundant, and better at obtaining food resources) over
management via translocation. immigrating non-resident species, especially where there is
Conservation translocation is a commonly used wildlife niche overlap between the two species (Massot et al. 1994).
management tool. Individual organisms are intentionally Habgood (2003) undertook experimental field trials on
transferred from one geographic location to another, where O. moco and O. aeneum on Tiritiri Matangi, to determine
the primary objective is for species or ecosystem conservation potential effects of interactions between resident and immigrant
benefit (IUCN 1987; IUCN/SSC 2013). This tool has been used species. This study was adapted from one of the research
for various reasons: 1) population restoration, via establishing priorities set in the Cyclodina spp. Skink Recovery Plan (Towns
populations within the species’ native range from which 1999). Habgood’s manipulation experiments showed that the
it has disappeared (reintroductions) or for supplementing resident species did not hold an incumbent advantage over
existing populations (reinforcement); and 2) conservation a newly introduced species with regard to body condition,
introduction of a species outside of its native range, to avoid movement, habitat use or mortality rate; suggesting it is
population extinctions (assisted colonisation) or to perform possible to establish new reptile species on Tiritiri Matangi.
an ecological function (ecological replacement) at the new However, precaution still needs to be exercised. Habgood
site (Griffith et al. 1989; Armstrong & Seddon 2008; Seddon (2003) recommended that any new reptile species be released
2010; IUCN/SSC 2013). Translocations are driven by many away from areas of high-density O. moco or O. aeneum
goals and ambitions. In New Zealand, the primary objective populations (i.e. away from grasslands).
of most conservation translocations is for establishment ofBaling et al.: Reptile research and conservation on Tiritiri Matangi Island 275
Table 1. The current status of reptile species resident (translocation and remnant populations) on Tiritiri Matangi Island, New Zealand.
__________________________________________________________________________________________________________________________________________________________________
Species Translocation Number of Source Reinforcement Current
date founders location status
__________________________________________________________________________________________________________________________________________________________________
Sphenodon punctatus 2003 60 Middle Island, None planned Breeding
Mercury Group
Hoplodactylus duvaucelii 2006 19 Korapuki Island, 2013 Breeding
Mercury Group
Woodworthia maculata - Remnant population Tiritiri Matangi Island None planned Expanding
Oligosoma smithi 2006 30 Tawharanui Regional Park 2010 Breeding
Oligosoma aeneum - Remnant population Tiritiri Matangi Island - Established
Oligosoma moco - Remnant population Tiritiri Matangi Island - Established
__________________________________________________________________________________________________________________________________________________________________
Ecological requirements of founder populations four adults captures. All this indicates that the proportion of
founders surviving on the island is likely to be very high. Body
Northern tuatara translocation 2003 condition and length of all re-captured individuals increased
An understanding of species’ ecological requirements is post-translocation, both in 2003–2005 and summer 2007/08
important for ensuring the success of a translocation because (van Winkel & Habgood 2009). These results were consistent
managers must be able to select suitable release sites to reduce with those of other S. punctatus translocations, most of which
the risk of failure (Griffith et al. 1989; Armstrong & McLean found high survivorship and increases in body condition over
1995; Meads 1995). However, the traditional approach of time (Ussher 1999; Merrifield 2002; Nelson et al. 2002).
using remnant habitat to predict species’ requirements may During 2005–2012, at least nine juveniles, one viable nest
be misleading because associations may reflect historical and three hatchlings were detected on the island. Gestation
(e.g. anthropogenic) events rather than a species’ optimal times and growth rates suggest that the juveniles were conceived
requirements (Gray & Craig 1991; Jones 2000). Thus, it is prior to translocation whereas the hatchlings were conceived on
important to test assumptions so a full range of release sites can Tiritiri Matangi (van Winkel & Habgood 2009). Although the
be considered and the most suitable site(s) selected (Armstrong absence of ground-nesting seabirds does not appear to affect
& McLean 1995; Ussher 2003). the short-term translocation success of S. punctatus on Tiritiri
Since Tiritiri Matangi Island largely lacks ground-nesting Matangi (criteria for short-term translocation success of S.
seabirds, the northern tuatara, S. punctatus reintroduction in punctatus are stated in Cree & Butler (1993)), it is uncertain
2003 (Table 1) provided an opportunity to test the assumption whether reproduction in the founder population is sufficient
that the presence of ground-nesting seabirds is a key factor for long-term persistence of this species on the island. Further,
in S. punctatus translocation success (Cree & Butler 1993; in the absence of experimental controls, it is unclear whether
Gaze 2001). This is an important consideration because many the translocation would have been more successful (i.e. with
islands proposed for S. punctatus restoration lack ground- higher survivorship, greater increases in body condition etc.)
nesting seabirds. All extant, stable S. punctatus populations had ground-nesting seabirds been present at the release sites.
coexist with large seabird colonies (Newman 1987; Cree et al.
1995). It has been suggested that co-habitation with seabirds Duvaucel’s gecko translocation 2006
may benefit S. punctatus in a number of ways: 1) through the Post-release behaviours may jeopardise translocation success
provision of burrows (Ussher 1999; Ussher 2003), 2) because if the occurrence of high frequency movements and large-scale
seabirds may increase the abundance of invertebrate prey (Walls dispersal from release sites reduce population density and
1978; Markwell 1998); and/or 3) through direct predation or consequently, expose the population to lower overall fitness or
scavenging of birds and eggs (Cartland et al. 1998; Blair et Allee effects (e.g. mate limitation, reduced population growth
al. 2000). Alternatively, co-habitation may just reflect shared and expansion) (Dennis 1989; Nunney & Campbell 1993).
ecological pressures, e.g. habitation restriction because rats Heightened activity levels may be energetically inefficient
have confined both S. punctatus and seabirds to island refugia (Reinert & Rupert 1999) and extensive dispersal increases
(Crook 1973; Cree & Butler 1993; Imber et al. 2000). vulnerability to predation while individuals move through
Ruffell (2005) aimed to test the hypothesis that burrow unfamiliar habitats (Sullivan et al. 2004). Both factors may
provision would increase S. punctatus translocation success reduce translocation success. Therefore, examining how a
by experimentally releasing S. punctatus into contrasting species responds to and utilises its new environment is important
sites; with and without artificial burrows. There were no for management of the species and improving the design of
ground-nesting seabird burrows at the experimental sites. future translocation projects (Germano 2006).
Results precluded this comparison, because S. punctatus Nineteen adult Duvaucel’s gecko, H.duvaucelii (10
failed to use the artificial burrows. Nevertheless, the release females, 9 males), were captured on Korapuki Island (Mercury
was still informative as to whether successful S. punctatus Island Group) and introduced to Tiritiri Matangi in December
translocations could occur in the absence of extensive ground- 2006 (Table 1) (van Winkel et al. 2010). van Winkel (2008)
nesting seabird colonies. A large proportion (38.3%) of the conducted intensive post-release monitoring of the geckos’
60 founders were captured 150 days or more after release, and movements and habitat preferences via radio-telemetry,
an even higher proportion (45%) of those were re-captured and tested the detection efficiency of a range of monitoring
in a survey five years later (van Winkel & Habgood 2009). techniques. Founders exhibited aberrant movements, often
A 2-hour opportunistic survey by Ussher in 2012 resulted in characterised by large-scale dispersal away from their release276 New Zealand Journal of Ecology, Vol. 37, No. 3, 2013
sites. This may reflect their unfamiliarity with the habitat competition between translocated and resident species (O. moco
and/or a drive to secure adequate resources. Hoplodactylus and O. aeneum), despite slight overlap in habitat use among
duvaucelii utilised habitat according to its availability on the all three species. Observations of founder and island-born
island. However, these results may have been confounded juvenile survival of the O. smithi population in 2009 confirms
by the founders’ aberrant movements and unfamiliarity with the short-term success of this translocation. This population
novel environments. seems capable of adapting to new habitat types, with apparent
Founder survivorship of H. duvaucelii was high. No rapid colour changes at the population level (either by natural
mortality was recorded 12 months post-release. A total of 22% selection or individual physical change).
(n = 6) of all recaptured individuals increased in body condition,
while the detection of island-born juveniles (from gravid female Avian predation
founders) with high body condition scores provided evidence Predation is a significant component of population dynamics,
of successful recruitment and acquisition of resources (i.e. trophic level and community ecology (Poulin et al. 2001)
food, shelter) by the juveniles. In addition, H. duvaucelii because it plays a vital role in regulating populations and
monitoring in 2009 detected seven individuals: two adult males, maintaining balance in ecosystem processes (Martín & López
two gravid females and three subadults (W. Ji, unpub. data). 1996; Zug et al. 2001). Predator-prey relationships typically
These results are promising for population establishment of H. evolve within natural communities, where prey populations
duvaucelii on Tiritiri Matangi. A population reinforcement of are generally robust enough to withstand the pressures from
90 geckos was undertaken in 2013 by Massey University, to natural predators (Bodini 1991). Translocated populations,
strengthen this establishment and increase population viability which generally consist of a limited number of individuals due
(i.e. genetic diversity). to ‘harvest’ restrictions based on source population size (Chau
2000; Pullin 2002; Begon et al. 2006; Dimond & Armstrong
Shore skink translocation 2006 2007), may not be as enduring as an abundant population of
Shore skinks, O. smithi, are widely distributed along the resident species. A translocated population with low founder
coastlines of the northern North Island and its offshore islands population size will be susceptible to stochastic events and other
(Towns et al. 2002; Hare et al. 2008; Chapple et al. 2009). biotic factors such as predation; where all can have a significant
This species’ body colouration is highly variable across its impact on the outcome of the translocation (Griffith et al. 1989;
geographical range and between habitats (e.g. light colour Saunders 1994; Armstrong & McLean 1995; Wolf et al. 1996).
morphology at white sandy beaches vs. dark colouration at Tiritiri Matangi, although free from mammalian predators,
rocky beaches). Such variation in body colours may represent supports high numbers of native birds known to prey upon
an ecological adaptation to the different habitat types for lizards (Haw & Clout 1999; Reid 2007). Even a small loss of
camouflage (Brown & Thorpe 1991; Bauwens & Castilla individual lizards via the predatory effects of birds can be a large
1998; Stuart-Fox et al. 2004). In frequently disturbed and proportional loss to a small founder population and thereby,
heterogeneous sites such as coastal habitats, the ability of a prey reduces the probability of population establishment. van Winkel
species to change colour (behaviourally or genetically through & Ji (2012) examined the potential impacts of avian predation
evolution) according to its environment can be important to on small translocated lizard populations by quantifying the rate
avoid predation. The reintroduction of O. smithi to Tiritiri of native bird predation on Tiritiri Matangi’s lizard fauna. The
Matangi (Baling et al. 2010) presented an opportunity to diets of a number of potential bird predators on the island were
assess the ability of these lizards to adapt and blend into new examined by analysing regurgitated pellets, stomach contents
habitat types. This may be important when considering future and nest materials, and by opportunistic observations of direct
translocations, especially if selection of source populations with predation on lizards.
phenotypic traits relevant to the release sites can influence the Kingfishers appear to be major predators of lizards on Tiritiri
probability of predation and hence founder survival. Matangi. A significant proportion (88%) of regurgitated pellets
A selection of light and dark-coloured O. smithi were contained remains of skinks (van Winkel & Ji 2012). No lizard
collected from mixed habitats (light-coloured sand and remains were recorded from any other bird species sampled
vegetation) at Tawharanui Regional Park, Auckland, and were during this study. This is contrary to past literature that reported
translocated to a beach with dark-coloured sand, vegetation and a variety of avian species preying on lizards (Marples 1942;
rocky habitats at Tiritiri Matangi (Table 1). The translocated Oliver 1955; Carroll 1966; Ramsay & Watt 1971; Whitaker
population was monitored every three months for a year and a 1991; Ball & Parrish 2005; O’Donnell & Hoare 2009) and
half, following release (2006–2008). The founder population suggested that many bird species opportunistically prey on
established successfully, with an overall capture rate of 2.42 lizards. Even opportunistic predation via by-catch may still
skinks/100 trap nights (TN) and a maximum of 8.00/100 TN be enough to affect a small founder population of K-strategist
in February 2008. Initial results showed high capture rates species (i.e. those slow to reach maturity, with low reproductive
of dark-coloured individuals. No light-coloured O. smithi rates). This strategy is characteristic of many of New Zealand’s
including those in juvenile stages, were found in any of the native and endangered lizard species (Towns 1991).
habitat types by 2007 (M. Baling, unpub. data). It is unknown
whether individuals physiologically changed to darker colours
or whether all the light-coloured animals failed to survive (e.g. Future reptile conservation and management
through predation). There was no direct evidence of avian
predation on O. smithi, however, New Zealand kingfishers Further reptile research
(Todiramphus sanctus vagans) are abundant at the release site. To date, research on Tiritiri Matangi Island’s reptiles has
Island-born O. smithi found yearly in 2007 to 2009 indicated only scratched the surface and further questions derived from
successful breeding and juvenile survival on the island, despite previous research still remain unanswered. For example, is
heavy storms and high tides during winters in all three years there a niche overlap in the dietary requirements of O. moco and
(M. Baling, unpub. data). There was no apparent aggression or O. aeneum? Niche overlap might create resource competitionBaling et al.: Reptile research and conservation on Tiritiri Matangi Island 277
between these two species (Habgood 2003) or with other (Towns & Daugherty 1994). In other words, the duration
translocated species such as O. smithi. Additionally, any level of long-term monitoring to detect success of a population’s
of intra- or inter-specific competition between resident and establishment and its eventual sustainability should depend
translocated populations may affect the island’s invertebrate on the life history characteristics of the reptile species itself
communities. Despite the high abundance of invertebrates (Dodd Jr & Seigel 1991), rather than human or funding-based
on the island (Clarke 2003), would this assemblage be able to timelines.
withstand the increasing predation pressures from both reptile
and avian biota? As for the avian populations on the island, Public participation
to what extent will they respond to new prey (reptile) species, Public involvement in the restoration of Tiritiri Matangi has been
or potentially another resource competitor? a critical feature of the island’s conservation success. Long-term
The influence of ecological restoration processes on research and monitoring programmes of biota on the island are
remnant species populations also needs to be monitored. also likely to benefit greatly from public involvement (Galbraith
Habgood (2003) questioned the potential negative effect of the & Hayson 1994; Parker 2008). Research and monitoring can be
large-scale tree planting revegetation scheme on resident skink costly in both labour and time. Experience to date shows that
species. Over time, vegetation change will reduce open habitats the public contributes to research and monitoring by providing
and consequently, may contract the range and abundance of voluntary labour to collect data and to generate funds. This is
resident species that prefer these habitat types (Timmins 1990; done mostly through the public community group: Supporters
Neill 1997). Approximately 40% of the island’s area has been of Tiritiri Matangi Incorporated (SoTM). Most long-term
retained as grassland, and this supports high densities of O. moco funding grants for research are awarded to projects that are of
and O. aeneum. These habitats have so far proven resilient to public interest and therefore, incorporating public participation
successional change (see other papers in this edition), however, or presentations are powerful strategies to ensure the success
this is no guarantee that such habitats will be maintained of a project (Galbraith & Hayson 1994; Towns et al. 2001).
naturally or through active management in the long term. So However, the public approach also has its downside; e.g.
in what percentages and over which areas will grasslands need purely theoretical studies may have less chance of attracting
to be maintained to sustain these lizard communities? As for the research funding because it is difficult to identify the tangible
rest of the island, the progression towards mature coastal broad- conservation or public interest outcomes for the island.
leaved forest will create new habitat types for forest-dwelling There is currently a long-term monitoring scheme for all
reptiles (Habgood 2003). Will translocations of species that translocated reptile species on Tiritiri Matangi. This monitoring
utilise those habitats be feasible when these new habitats are scheme aims to confirm self-sustaining populations for all
available? Or can species traditionally associated with climax translocated species by obtaining periodic field records of
forest and seabird communities elsewhere also survive and population abundance, distribution and breeding. Information
establish in the grassland and shrubland successional plant gathered from this scheme can also be used to guide future
communities on the island? management. The collaboration between the SoTM and reptile
Population size of founder and remnant species have been researchers from Massey University includes the provision of
shown to be important in population persistence (Vucetich & training and leadership responsibilities to SoTM volunteers
Waite 2001; Briskie & Mackintosh 2004; Jamieson et al. 2006; so they can conduct methodical reptile surveys. This sense of
Miller et al. 2009). However, currently there is no baseline joint ownership in managing reptile monitoring projects will
information on genetic diversity of either the translocated or bring together the knowledge and efforts of the scientists and
resident species, so how population genetics will affect their volunteers. In doing so, it provides a method for collecting
fitness and consequent long-term success is uncertain. There essential information that will be well informed and can be
have been two reinforcements of the translocated populations (H. relayed to the public via SoTM volunteers.
duvaucelii and O. smithi) to increase their effective population Participation in research and monitoring projects will
sizes on Tiritiri Matangi (Table 1). Despite the current lack in also give the public a sense of realistic approaches and
knowledge of the species’ population genetic structures, these timelines for conservation work. Quite often, only successful
reinforcements will increase genetic diversity by having large translocations are reported by the media and consequently, this
founder population sizes and should improve the chances of tends to portray translocation as a very effective conservation
population establishment. strategy. Experience elsewhere indicates this creates unrealistic
Long-term monitoring should be a standard requirement expectations of translocation outcomes, leading the public to
for New Zealand reptile management. Sphenodon punctatus expect it to be employed more often in the future as a quick
and other large New Zealand lizards, such as H. duvaucelii, are fix to ecological problems (Craig & Veitch 1990; Dodd Jr &
K-strategists (Cree 1994; Bannock et al. 1999) and will exhibit Seigel 1991; Reinnert 1991). The public need to be made
slow responses to ecological changes, including translocation aware that many translocations do fail and hard work over long
outcomes. For example, the current evidence of juvenile periods of time is required to achieve translocation success.
S. punctatus recruitment on Tiritiri Matangi only represents Collaboration between scientists and conservation volunteer
the first generation offspring from founders (van Winkel & groups like SoTM will be one of the key solutions that will
Habgood 2009). An indicator of translocation success is the deliver this information to the rest of the New Zealand public.
confirmation of second-generation offspring, and so in the
case of S. punctatus, this may take up to another 20 years to
confirm (Seddon 2009). Another example is the monitoring
of the endangered O. whitakeri (Whitaker’s skink) that went Conclusion
for over nine years before there was significant evidence of
population expansion on Korapuki Island (Towns & Ferreira Current research on Tiritiri Matangi Island has increased the
2001). Population expansion for many endemic New Zealand baseline knowledge of reptile populations and their role in
lizard species has been predicted to be less than 10% per year the island’s ecological processes. Many opportunities are278 New Zealand Journal of Ecology, Vol. 37, No. 3, 2013
still available for research to be conducted on this accessible Zealand lizard species within the Hauraki Gulf. New
island. There should be a continued emphasis on experimental, Zealand Journal of Zoology 40: 249–254. DOI: 10.1080/
research-based approaches for any future reptile conservation 03014223.2012.747970
translocations. Finally, conservation efforts should not only Ball O, Parrish R 2005. Lizard predation by North Island
focus on ecologically significant offshore islands (Craig & fernbird (Bowdleria punctata vealae). Notornis 52:
Veitch 1990). The development, restoration and protection 250–251.
of highly-modified environments (usually considered of low Bannock CA, Whitaker AH, Hickling GJ 1999. Extreme
biological value), as was the case for Tiritiri Matangi, not longevity of the common gecko (Hoplodactylus maculatus)
only provide opportunities for threatened species recovery on Motunau Island, Canterbury, New Zealand. New
without expense or risk to the original population, but also Zealand Journal of Ecology 23: 101–103.
offer community groups and the general public the chance to Bauwens D, Castilla AM 1998. Ontogenic, sexual and
be directly involved in reptile conservation. microgeographic variation in color pattern within a
population of the lizard Podarcis lilfordi. Journal of
Herpetology 32: 581–586.
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for their continued long-term support of reptile research on triacylglycerol and cholesterol of the tuatara (Sphenodon
Tiritiri Matangi. Research and translocations were funded punctatus punctatus) from islands differing in the presence
by the Supporters of Tiritiri Matangi Inc. Research Fund (S. of rats and the abundance of seabirds. Journal of the
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